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The redevlopment of St Pancras used offsite technologies
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Offsite manufacturing can significantly reduce waste
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In today’s carbon-conscious society, no area of construction is immune from the need to reduce the impact of the built environment and the build process itself. Historically, construction has been perceived as a highly wasteful activity involving huge demands on scarce, non-renewable resources. Add to this the concern that the actual use of our buildings represents a quarter of all CO 2 emissions, it is hardly surprising that construction suffers a serious image problem when it comes to sustainability.
Extreme makeover
In its quest for a thorough image makeover, the industry is searching for solutions that will improve this position, both in terms of perception and the practical reality of reducing carbon emissions. This frenetic search for answers inevitably leads to quick fix options that seem to involve the latest gadgets and gismos that are more image than substance. There is also a suspicion that in many cases the carbon impact of producing the 'eco bling' could be many times more than the carbon it might save during its service life.
Factory finish
So we need to look at other options for the construction industry that deliver our needs in a more sustainable way. For newbuild construction this involves making ever greater use of factory build technology to replace the traditional onsite build approach. Interestingly, offsite construction has not enjoyed a good press for its sustainability performance, largely because of a view that if it is not produced onsite then it isn’t environmentally friendly.
Evidence base
We thought it important to understand and establish the true facts of what is quite a complex question – what is the environmental impact of building using offsite technology compared with the traditional site-based approach? Over the last five years we have invested significant resources into researching the evidence that either refutes or confirms our belief that factory methods are ultimately more sustainable than traditional site based.
Research findings
At this year’s Greenbuild Expo event to be held at Manchester Central from 26th to 27th May we will be presenting our findings in full. Whilst our research and evidence gathering will continue for some time, there is already clear evidence that offsite construction can bring significant environmental benefits both at the embodied energy level and in the long-term use of the building.
Beyond the build
It is very important to retain a holistic view of environmental performance to gather the complete whole-life picture of environmental impact, but it is worth considering some of the key areas of construction performance to understand how offsite technology can deliver lower impact solutions.
As part of our research, we undertook a study into the waste performance of a range of offsite techniques to compare them directly with traditional construction. This study was undertaken in conjunction with WRAP and it identified that from the same resource start point (offsite construction materials are in many cases the same as traditional), offsite manufacturing generated less than 10% of the raw material waste that conventional construction methods typically achieve to bring the building to the same point of completion.
Ongoing project
Our research continues, with a view to establish that once onsite these offsite technologies continue or maintain this significant reduction in raw material waste. Initial results look promising as offsite manufacturers seek to reduce packaging waste by using returnable component protection systems, and limit the onsite activities required to integrate the factory produced elements into the construction.
The study shows a very clear correlation between site activity (hours of labour) and the use of raw materials to rising levels of waste, clear evidence of the need to remove the traditional site operations into a factory environment in order to save our scarce resources.
Material transportation
Another key area for factory technique investigation is the question of transport miles and CO 2 emissions related to moving the raw materials and creating the finished construction onsite. This research is continuing and, contrary to what you might imagine, making large elements of the construction in a factory and transporting this to site has a significant reduction in overall transport miles and CO 2 emissions.
This is not a surprise to those who use offsite systems on a regular basis. A short study of a London apartment project, built using factory finished volumetric modules for the apartments, established that for this particular scheme there were 90% fewer onsite vehicle deliveries compared with what we anticipated using conventional build methods, with the reduction in part load deliveries the most staggering find.
Lifetime costs
Part of the research is also identifying the impact of factory based construction through the service life of the building. For a building that may be in use for over 100 years, the lifetime emissions can far outweigh the embodied energy emissions. It is important therefore to establish how offsite techniques affect this aspect of performance.
And the initial research is very encouraging. Our studies show that offsite techniques can dramatically reduce air infiltration rates and, what is perhaps more important, maintain this level of performance (airtightness) over the lifetime of the building. Using factory build methods, airtightness levels for the fabric of the building of less than 1 m 3/m 2/hr are readily achievable and allow the building designer to achieve high levels of control of the internal environment without over specifying the plant and equipment.
Holistic approach
There are clearly many more criteria involved when considering the total picture of sustainability performance including local employment and up-skilling, health and safety, quality of life issues and end-of-life reuse or recycling.
Our research on these issues is continuing and we plan to present further findings at the conference. To hear more and join in the debate, sign up free on the Greenbuild Expo website.
Martin Goss is MD of specialist offsite consultancy Mtech Consult. For further information visit www.mtech-consult.com.
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